Nineteen years ago, Raymond Burk, M.D., took his first 12-hour-long train ride to a remote corner of
southwest China to study a unique population of people whose diets are deficient in the essential mineral selenium.

Because the soil in this area is
low in selenium, so are the locally grown vegetables. Selenium deficiency contributes to a potentially fatal form of cardiomyopathy, an inflammation of the
heart muscle called Keshan disease.

Until the connection between diet and Keshan disease was established in the 1970s, people in this region
“were just scared to death,” says Burk, professor of Medicine and Pathology at Vanderbilt.

“It was sort of like polio in the U.S.
back in the ’40s and ’50s,” Burk says. “People tried to keep their kids from going to swimming pools … In the affected areas of
China, They would send their children to live in areas where this disease did not occur.”

The incidence of Keshan disease has declined among the
325,000 residents of Mianning County in the foothills of the Tibetan Plateau, thanks to the importation of selenium-rich vegetables from neighboring
regions.

Yet selenium deficiency persists. Burk and Kristina Hill, Ph.D., research associate professor of Medicine at Vanderbilt, and their colleagues
in China are trying to determine the best way to correct it through dietary supplementation.

The recommended dietary allowance (RDA) for selenium in
the United States is based on the concentration of a blood “biomarker” called glutathione peroxidase. Another biomarker, selenoprotein P, may be
more accurate, however.

The researchers discovered that longer periods of supplementation are needed to raise selenoprotein P levels compared to
glutathione peroxidase. Plasma glutathione peroxidase is likely a biomarker primarily for selenium in the kidney, they concluded, whereas selenoprotein P
reflects selenium levels in the whole body.

While further study is needed, these results suggest that the RDA for selenium should be based on
selenoprotein P, rather than glutathione peroxidase, the researchers reported last year.

Traveling to Mianning County is still no picnic, but Burk no
longer has to spend 12 hours on the train – today he can fly to nearby Xichang.